Sun Occultation Mission with Solar Sails

Context:

Studying the solar corona is fundamental to gain an insight into a plethora of
phenomena with major impact on satellite dynamics and operations. Due to the very-
modest brightness of the corona, observations are achieved by means of coronagraphs,
which are optical instruments provided with a mask to occult the Sun’s disk. However,
ground-based measurements suffer from scattering due to the atmosphere. Quality of
the observations can be improved by using large masks placed far away of the
telescope’s detector. This is why total solar eclipses offer great opportunities to carry
out ground-based observations. Nonetheless, eclipse events are extremely rare and last
only few minutes. A novel concept was recently proposed, which consists of using
natural bodies as occulting disks. The idea is to place a satellite in proximity of the tip
of the umbra cone generated by a celestial body (referred to as “observation zone”). In
this way, high-resolution long-lasting observations are possible with relaxed
requirements on position accuracy. Assuming that electrical power is gathered via solar
panels, the satellite is constrained to periodically leave the observation zone and
expose itself to sunlight to recharge its batteries. However, a preliminary study using
the Earth as an occulting body revealed that chemical and micro propulsion systems
may strongly limit the number of transitions from/to the observation zone since the ∆V
of a single cycle is of the order of various hundreds of meters per second. Alternatively,
the possibility of using a solar sail to maneuver the satellite in a propellantless fashion
was suggested.

Objectives of the stage:

The objective of the stage is a feasibility analysis on the exploitation of solar sails to
carry out the aforementioned mission. The circular restricted three-body problem will
be used to model the motion of the sail. Trajectory design will be formulated as a
periodic optimal control problem aimed at maximizing the duty cycle of the
observations, defined as the fraction of orbital period devoted to observations. Charge
of the batteries will be part of the state variables. After formulating the problem, the
student will apply the Pontryagin maximum principle (PMP) to deduce necessary
conditions of optimality. Numerical solution will be achieved by using indirect
techniques. The ct software will be used to this purpose (https://ct.gitlabpages.inria.fr/gallery/).

Work environment:

For Master 1 or Master 2 students. The internship will take place in 2022 and it will last 4 to 6 months.

Advisors: Alesia Herasimenka, Jean-Baptiste Pomet

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